hyphen with prefixes

Most prefixes join the word with no hyphen: reenter, prewar, nonprofit. Use a hyphen in three cases. The first is when a prefix ending in a or i meets a word that begins with the same letter, as in anti-inflammatory and intra-arterial. The second is when the closed form would read as a different word, as in re-sign (sign again) vs. resign (quit). The third is before a capitalized word, as in pre-Columbian and mid-July. In a title, capitalize the prefix but not the word after the hyphen, unless that word is a proper noun.